From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59541) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cc0H8-0004Mm-4H for qemu-devel@nongnu.org; Thu, 09 Feb 2017 20:45:27 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cc0H5-0006ip-2R for qemu-devel@nongnu.org; Thu, 09 Feb 2017 20:45:26 -0500 Received: from mail-yb0-x241.google.com ([2607:f8b0:4002:c09::241]:35543) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1cc0H4-0006iB-TA for qemu-devel@nongnu.org; Thu, 09 Feb 2017 20:45:22 -0500 Received: by mail-yb0-x241.google.com with SMTP id j82so853275ybg.2 for ; Thu, 09 Feb 2017 17:45:21 -0800 (PST) From: Pranith Kumar Date: Thu, 9 Feb 2017 20:45:19 -0500 Message-Id: <20170210014519.12413-1-bobby.prani@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Subject: [Qemu-devel] [PATCH] tcg: handle EXCP_ATOMIC exception properly List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini , Peter Crosthwaite , Richard Henderson , "open list:Overall" Cc: =?UTF-8?q?Alex=20Benn=C3=A9e?= The current method of executing atomic code in a guest uses cpu_exec_step_atomic() from the outermost loop. This causes an abort() when single stepping over atomic code since debug exception longjmp will point to the the setlongjmp in cpu_exec(). Another issue with this mechanism is that the flags which were set in atomic execution will be lost since we do not call cpu_exec_enter(). The following patch moves atomic exception handling to the exception handler where all these issues are taken care of. The change in start_exclusive() is necessary since now the cpu in atomic execution will have its running flag set, but we do not want to count it as pending. Thanks to Alex for helping me debug the issue. CC: Alex Bennée CC: Richard Henderson CC: Paolo Bonzini Signed-off-by: Pranith Kumar --- cpu-exec.c | 2 ++ cpus-common.c | 2 +- cpus.c | 4 ---- 3 files changed, 3 insertions(+), 5 deletions(-) diff --git a/cpu-exec.c b/cpu-exec.c index b0ddada8c1..dceacfc5dd 100644 --- a/cpu-exec.c +++ b/cpu-exec.c @@ -427,6 +427,8 @@ static inline bool cpu_handle_exception(CPUState *cpu, int *ret) *ret = cpu->exception_index; if (*ret == EXCP_DEBUG) { cpu_handle_debug_exception(cpu); + } else if (*ret == EXCP_ATOMIC) { + cpu_exec_step_atomic(cpu); } cpu->exception_index = -1; return true; diff --git a/cpus-common.c b/cpus-common.c index 59f751ecf9..7b859752ea 100644 --- a/cpus-common.c +++ b/cpus-common.c @@ -192,7 +192,7 @@ void start_exclusive(void) smp_mb(); running_cpus = 0; CPU_FOREACH(other_cpu) { - if (atomic_read(&other_cpu->running)) { + if (atomic_read(&other_cpu->running) && !qemu_cpu_is_self(other_cpu)) { other_cpu->has_waiter = true; running_cpus++; qemu_cpu_kick(other_cpu); diff --git a/cpus.c b/cpus.c index e1b82bcd49..981f23d52b 100644 --- a/cpus.c +++ b/cpus.c @@ -1461,10 +1461,6 @@ static void *qemu_tcg_cpu_thread_fn(void *arg) */ g_assert(cpu->halted); break; - case EXCP_ATOMIC: - qemu_mutex_unlock_iothread(); - cpu_exec_step_atomic(cpu); - qemu_mutex_lock_iothread(); default: /* Ignore everything else? */ break; -- 2.11.0